insufficient contiguous memory was available to service the allocation request

[michaelhenkel]

Hi there,

I'm trying to allocate an obscene amount of memory (2 Gbyte) but my program crashes with

insufficient contiguous memory was available to service the allocation request

this is the relevant code snippet:

            let layout = Layout::from_size_align(request.message_size as usize, 1).unwrap();
            let mut lmr = match rdma.alloc_local_mr(layout){
                Ok(lmr) => lmr,
                Err(e) => {
                    panic!("alloc_local_mr error: {}", e);
                }
            };

request.message_size is set to 2 Gbyte.
My machine has plenty of RAM (256 GB) and I freshly rebooted hoping to have more contiguous memory available. I also enabled CMA (Contiguous Memory Allocator) and reserved 50 Gbyte but that didn't help.
I also tried to concurrently allocate multiple 1 Gbyte memory areas, leading to the same effect.
I don't believe that my machine has <2 Gbyte contiguous memory right after a reboot.
Any ideas?

Thanks